A polyester fiber represented by polyethylene terephthalate (hereafter referred to as PET) has been used in wide applications without limiting to clothing and materials, because of having superior mechanical characteristics and handling property. Accordingly there have been investigated many developments of fibers and products satisfying required characteristics in response to various kinds of applications.
In clothing and materials, composed of a woven/knitted product containing the polyester fiber, abrasion resistance is one of important characteristics required, and the woven/knitted product superior in abrasion, resistance has been required.
In the case where the polyester fiber is used mainly in a form of the woven/knitted product, in clothing, in particular, an outdoor clothing such as a windbreaker, a down jacket, there may be the case generating fuzz or tearing caused by rubbing in wearing at side parts or thigh parts. In addition, in the case where it is used particularly in an outdoor wear (a wear for outdoor activity such as for mountain climbing, camping), there may be the case generating fuzz or tearing caused by severe friction with other objects (for example, friction with a rucksack, a rope or the like, or rubbing with a ground, a cliff, a plant or the like).
In the case where the polyester fiber is used for clothing mainly in a form of a knitted product, in particular, for a sports wear such as a game shirt, pants, there may be the case generating fuzz or tearing caused by severe friction with itself or other objects (for example, contact with competitors themselves or sports goods, or contact with a ground in sliding or the like).
Generally in view of abrasion, the polyester fiber has been known to be inferior a little bit as compared with a polyamide fiber such as nylon 66, however, the polyamide fiber easily fends to generate photodegradation or yellowing, and is thus not suitable for applications to be used in outdoors under severe condition. Under such a circumstance, various investigations have been promoted to improve abrasion resistance in the polyester fiber.
Conventionally, a method has been known for obtaining a high strength polyester by increasing draw ratio. In addition, the following PATENT LITERATURE 1 has disclosed a method for obtaining a high strength polyester fiber by contriving a drawing method in producing the polyester fiber. Although yarns obtained by these production methods have high strength in a fiber axis direction, they are weak against external force from other direction such as a direction perpendicular to the fiber axis, and thus cannot provide sufficient abrasion resistance in the case where abrasion occurs from all directions such as abrasion of a clothing material.
The following PATENT LITERATURE 2 has proposed a crimped yarn superior in abrasion resistance for clothing, having a flat cross-section, with enhanced intrinsic viscosity and strength. This crimped yarn is considered to be used for clothing, having a structure with enhanced strength or orientation, and is thus brittle in a direction other than the fiber axis, and has not sufficient durability against friction caused from all directions.
Various methods for enhancing abrasion resistance, by adding additives and the like to a polymer, have also been devised. For example, the following PATENT LITERATURE 3 has proposed a fiber having enhanced orientation due to a specific crystal structure by containing special silicon oxide particles.
However, containment of such particles generally results in decrease in yarn strength. In addition, due to having a structure with enhanced orientation, it is still brittle in a direction other than the fiber axis, and is not sufficient in abrasion resistance in all directions, such as Martindale abrasion.
The following PATENT LITERATURE 4 has proposed a method for improving abrasion resistance, by performing refluxing heat treatment of 0.2 to 5% and fluid interlacing treatment after drawing a non-drawn polyester yarn, to suppress single yarn breakage and generation of fuzz caused by friction of yarns themselves of interlace yarn, which is used in a warp of the woven product, and with metal parts of a weaving machine.
However, this method is capable of suppressing, to some extent, single yarn breakage or generation of fuzz caused by friction between the yarn and a weaving machine parts in producing the woven product, it was difficult to prevent tearing caused by severe friction with clothing itself or other objects, in an wear, in particular, an outdoor wear such as a windbreaker, a down jacket, a sports wear such as a game shirt or pants, or an outdoor wear (such as a wear for outdoor activity such as for mountain climbing, camping) or the like.
In particular, in recent years, in view of good comfort derived from “lightness of cloth” (light weight per unit area of the cloth), needs for making a woven/knitted product thin cloth has been increasing. In order to make the woven/knitted product thin cloth, it may be enough to use fine size fiber, however, the finer size fiber to be used tends to decrease abrasion resistance of the woven/knitted product the more. Accordingly, in recent years, requirement for enhancement of abrasion resistance in the fine size fiber has been increasing more and more.